When you handle the CellToolTipTextNeeded event, the ToolTip text you specify in the handler is shown whenever the mouse pointer is over a cell and the control ShowCellToolTips property value is true. The CellToolTipTextNeeded event is useful when you want to display ToolTips determined by the current state or value of a cell.

You can use the ColumnIndex and RowIndex properties to determine the state or value of a cell, and use this information to set the ToolTipText property. This property is initialized with the value of the cell ToolTipText property, which the event value overrides.